1. Field of the Invention
The present invention relates to a gas sparging method for absorbing a component of a gas in a liquid or for effecting a gas-liquid reaction by gas-liquid contact.
2. Description of the Prior Art
There is known a bubbling tower in which a gas is introduced into a liquid and the gas is dispersed in the liquid in the form of fine bubbles to increase the gas-liquid contact interface area. Such tower has a gas sparger for dispersing the gas into the liquid.
As such gas sparger, there are ordinarily adopted: (1) a sparger composed of a porous material such as a sintered metal, or (2) a sparger comprising a perforated plate or a perforated pipe having the ends blocked.
A sparger of the first type composed of a sintered metal or other porous material is advantageous in that fine bubbles can be generated and the contact area can be increased, but this sparger is defective in that the treatment capacity is small, the pressure loss is extreme and clogging or jamming readily occurs.
A sparger of the second type comprising a perforated plate is broadly used, but since it is dipped in the liquid, the gas must pass through the liquid before it is dispersed, and there is inevitably brought about a disadvantage because resistance to gas introduction is very large. Further, with increase of the quantity of the gas being treated, there is caused a so-called sloshing phenomenon in which the liquid containing gas bubbles repeats a large horizontal movement periodically.
This sloshing phenomenon of the liquid 2 in a bubbling tower 1 will now be described conceptually by reference to FIGS. 1-A, 1-B, 2-A and 2-B. The liquid level 2A inclined with respect to the horizontal direction is changed from the state shown in FIG. 1-A to the state shown in FIG. 1-B. Further, the concave liquid face 2B shown in FIG. 2-A is changed to the convex liquid face 2C shown in FIG. 2-B. In practice, changes of the liquid level are more complicated. If such changes of the liquid level are extreme, the gas-liquid contact time is varied according to the gas-jetting position and the gas-liquid contact efficiency is reduced. Further, because of extreme changes of the liquid level, it becomes difficult or impossible to operate the apparatus stably. If it is intended to conduct the operation stably, the quantity of the gas to be introduced should be controlled at a low level and it becomes impossible to fully utilize the treating capacity of the gas-liquid contact apparatus. Still further, the apparatus per se should be designed and constructed so that it can resist most violent changes of the liquid level or most violent sloshing phenomenon without any trouble or difficulty or disorder in the apparatus.
A gas sparger of the porous pipe type comprises an end-blocked linear or ring-like pipe having a great number of small holes formed on the top or bottom or the side face. When such sparger is used, it is maintained in the horizontal state and the gas is spouted out from said small holes. Also this porous pipe sparger includes a region where sloshing is caused with increase of the amount of the gas being treated as in case of the above-mentioned porous plate sparger. If the liquid is a slurry containing solids suspended therein, when introduction of the gas is stopped, the slurry intrudes into the pipe through the small holes and the solids in the slurry adhere to the pipe wall to form scales. When the operation is started again, such scales of the solids do not flow out completely, thereby causing the pipe to become clogged with the solids.
Accordingly, there has been a need for the elimination of the foregoing defects and disadvantages in known gas spargers.